Project Summary/Abstract Data suggest that approximately 40% of the 5.5+ million older Americans with Alzheimer's disease (AD) suffer from severe dysfunction of sleep?wake and circadian systems. In people with mild cognitive impairment (MCI), which is an ?at risk? or potential prodromal stage of dementia, sleep-wake disturbance is evident in up to 60% of patients. Sleep is critical for healthy cognitive processing in older adults. This application proposes to investigate the impact of a long-term lighting treatment on sleep physiology and sleep-dependent cognitive processes in MCI and mild AD patients. We hypothesize that a long-term (6-month) lighting intervention technology (LIT) designed to promote circadian entrainment will improve sleep and, thus cognition. We also hypothesize that LIT will improve depression and quality of life (QoL). In a single-arm, randomized, placebo-controlled (non-active comparison lighting intervention), between-subjects study, we will investigate the effect of a 6-month exposure to LIT (with a ?pure follow-up period? of 3 months post-intervention) on: (1) objective measures of sleep (EEG, actigraphy), (2) subjective measures of sleep (Pittsburgh Sleep Quality Index), (3) cognition (working and long-term memory), and (4) depression and QoL (questionnaires). Our scientific premise is that sleep spindles, and timing of spindles relative to SO, are critical components of an interaction between electrophysiological events that provide a mechanistic explanation for memory consolidation during sleep in young and older adults. Data from the current grant by the co-PI shows that LIT improves sleep (measured via actigraphy and questionnaires), depression and agitation in late stages AD patients. The current grant is a logical extension of the co-PIs work: it will include MCI and mild AD patients and it will measure EEG and cognitive performance, none of which are included in the current grant activities. In addition to improving patients? lives, LIT has the potential to reduce burden on caregivers. Thus, an exploratory goal is to also measure the impact of LIT on caregivers? sleep, cognition, depression, and quality of life. We will demonstrate that a practical, effective, tailored, nonpharmacological LIT can be used to improve sleep, cognition, and quality of life in older adults with MCI and mild AD living at home or in independent or assisted living facilities, thereby possibly mitigating significant financial and social burdens. The proposed work is significant because it will be the first to investigate the relationship between long-term use of light therapy, a safe and easy to use intervention, and sleep and cognition in MCI and mild AD patients, as well as its impact on caretakers. Given evidence linking the sleep?s importance in the development of AD, the proposed studies can have a significant impact on the progression of MCI and mild AD, and caregivers? quality of life.